Fernando “Frank” Caldeiro, who was a member of NASA's Astronaut Class of 1996, died Saturday after battling a brain tumor for two and a half years. He was 51.

Although he never flew into orbit aboard the shuttle or space station, most recently Caldeiro directed the operation of high-altitude atmospheric research experiments carried on board the NASA WB-57, which can fly higher than 60,000 feet.

“Frank was a valued member of the astronaut corps and the Flight Crew Operations team,” said astronaut Brent Jett, director of Flight Crew Operations. “He provided a wealth of experience and made significant contributions to the success of both the WB-57 project and the Space Shuttle Program. He will be missed by all those who knew him at NASA. Our hearts go out to his family.”

Born on June 12, 1958, in Buenos Aires, Argentina, Caldeiro considered New York City and Merritt Island, Fla., his hometowns.

After earning his undergraduate degree, Caldeiro worked as a test director on the Rockwell/USAF B-1B Bomber, and in 1988 Rockwell International transferred him to the Kennedy Space Center to work on the space shuttle's main propulsion system.

Three years later, Caldeiro joined NASA at Kennedy Space Center as a cryogenics and propulsion systems expert for the safety and mission assurance office.

After being selected as an astronaut in 1996, Caldeiro qualified for flight assignment as a mission specialist, although it often takes years to receive a flight assignment. He was Argentina's first astronaut.

Working at Johnson Space Center, he served as the lead astronaut of the International Space Station's Environmental Controls and Life Support Systems and the European-built station modules. In that role he was involved in all aspects of design and manufacturing of Node 2, Columbus Module and the Cupola components of the space station.